RunKeeper provides useful info as you run, then uploads it to the RunKeeper site.

Can I gush? RunKeeper is the coolest freakin' iPhone application ever. OK, maybe not for everyone, but it's definitely the coolest for runners, hikers, bikers, and anyone else interesting in tracking their outdoor activities.

Let me explain. This summer the running bug bit me hard, and I'm now running farther and faster than in years past. Consequently, I've grown interested in determining my pace, distance, total run time, and so on.

My first thought was to get Apple's Nike + iPod, which is reasonable at $29--but incompatible with my iPhone 3G. Plus, I didn't want to have to buy a pair of Nike+ shoes or "hack" the Apple sensor to latch onto my own shoes.

All this happens in real-time as you run, but where it really gets cool is at the end: When you tap Save Run, RunKeeper quickly uploads that data to the eponymous Web site, where you can track all your runs and get very specific information about each (such as how fast you were going at any particular point along the way). You also get to see your exact route on a map. It's really, really cool.

You can, of course, play your music while RunKeeper is running, and the app recently added integration with Facebook and Twitter (for those who like to crow about their runs).

I wasn't sure I wanted to carry my relatively big, bulky iPhone with me when I was accustomed to something Shuffle-size. But it happened to fit just perfectly in an old Zune armband case, and obviously, it's great to have both a phone and a GPS with me in case of emergency.

I'm using ad-supported RunKeeper free, which suits me fine. There's a $9.99 Pro version that offers audio cues and support for custom workouts (based on time, distance, and so on)--closer to what you get from Nike+iPod.